In line marked with 1 we tell to Vagrant that use Vagrant’s default insecure key inside the machine. In the next line (2) we specify the paths to the private keys to use to SSH into the guest machine. In step number 3 we copy our id_rsa.pub into the Vagrant machine and rename as authorized_keys. And finally, in step 4 we change the configuration of sshd, for not asking a password and restart our service.

Finally we can access to our Vagrant machine with pure ssh vagrant@192.168.15.200.